Sunrise 6:02 AM   Sunset 8:05 PM Moonrise 2:46 AM   Moonset 2:05 PM

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FXUS66 KSTO 032056 AFDSTO

Area Forecast Discussion National Weather Service Sacramento CA 156 PM PDT Fri May 3 2024


SYNOPSIS
DRY AND WARM WEATHER TODAY WITH LOCALLY BREEZY NORTHERLY WINDS.
ACTIVE WEATHER RETURNS THIS WEEKEND AS A WEATHER SYSTEM MOVES INTO THE AREA BRINGING SHOWERS, MOUNTAIN SNOW, ISOLATED THUNDERSTORMS, GUSTY WINDS AND MUCH COOLER TEMPERATURES.

Sunny and pleasant conditions prevail across interior NorCal this afternoon, with some breezy northerly winds being observed in the Valley. Our next weather system is approaching the area from the Gulf of Alaska and is expected to bring widespread rain showers, mountain snow, isolated thunderstorms, gusty southwest winds, and much cooler temperatures on Saturday.

Model guidance shows an anomalously deep and cold closed low moving into the PacNW Saturday morning. Precipitation first looks to begin in far northwestern California early Saturday morning then spread inland throughout the day. Latest forecast rainfall totals remain around 0.50" to 1.30" inches for the Valley and around 1" to 3" inches in the foothills and mountains. With the track of the low forecast to move over northern part of California, there will be a risk of isolated thunderstorms to develop Saturday afternoon and evening. There exists a 15-25% probability of thunderstorm development, with the better chances north of I-80. Any thunderstorms that do form could bring locally heavy rainfall, dangerous lightning, gusty winds, small hail, and possible funnel clouds.

The Winter Weather Advisory has been upgraded to a Winter Storm Warning, with the timeframe remaining the same, from 11 AM Saturday until 8 AM PDT Sunday. Snow, heavy at times, is expected mainly for elevations higher than 5000 feet. Total snow accumulations forecast are around 5 to 12 inches, with locally higher amounts at the highest elevations. NBM probabilities of exceeding 12" inches of snowfall are at around 60-80% along the I-80 corridor. Winds will also be gusting from 30 to 50 mph out of the southwest. Snow levels will be at around 4000-5000 feet Saturday afternoon, and lower as the system moves through the area to around 3000 feet on Sunday. Snowfall rates of 1-2" inches per hour are possible, mainly from around 10 AM to 10 PM Saturday as the bulk of the precipitation moves through. Snow covered roads, reduced visibilities, and chain controls are all likely. If you must travel this weekend, make sure to check road conditions at quickmap.dot.ca.gov before heading out.

Gusty winds will also begin to develop later tonight through Saturday as the system moves closer to the area. The NBM projects around a 55-90% probability of wind gusts greater than 40 mph in the northern/central Sacramento Valley and northeast foothills.
Today is a great day to secure any loose outdoor items to prepare for the potential of gutsy winds.

Precipitation should move through the area relatively quickly, with most of the heavier rain/snow ending by Sunday morning. A noticeable sensible weather impact from this system will be the drop in high temperatures around the region. Saturday, we can expect temperatures to be around 10-20 degrees cooler than today's high temps. Sunday we will start to slightly recover temperature wise as the closed low moves further off to the east, with highs in the mid 60s for the Valley and mid 30s to low 50s for higher elevations. Monday, our high temperatures will climb back into the low 70s for the Valley, with off-shore ridging beginning to develop in the Pacific.

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...

Broad upper level troughing from the Pacific Northwest toward the central Plains looks to remain in place through midweek. This will induce continued northwesterly flow across interior NorCal during the extended forecast period. A reinforcing shortwave looks to travel through this flow pattern Tuesday into Wednesday, gradually deepening the trough (and potentially retrograding it) through the late week period. While precipitation impacts look to remain displaced to the north and east of the region, this pattern looks favorable for northerly surface winds to set up from Tuesday through Friday of next week. Exact details such as timing and magnitude of the winds is still somewhat uncertain, but ensemble guidance is coming into agreement on a dry, warm, and windy pattern setting up mid to late next week. Strongest winds, with gusts to 40 mph or greater, are expected on Wednesday and Thursday, with still breezy to locally gusty winds on Tuesday and Friday respectively.

AVIATION

VFR conditions over interior NorCal until around 08z Saturday then areas of MVFR/IFR becoming widespread as weather system moves into the area. Local LIFR over mountains in precipitation. For the Valley, surface winds at or below 12 knots until around 08z, then southerly winds of 15-30 knots with local gusts 40 knots possible.
Over the mountains, southwesterly wind gusts of 40-50 knots possible.

STO WATCHES/WARNINGS/ADVISORIES
Winter Storm Warning from 11 AM Saturday to 8 AM PDT Sunday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park.

Sacramento #4
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Fri -- 03:43 AM PDT     Moonrise
Fri -- 04:23 AM PDT     2.41 feet High Tide
Fri -- 06:05 AM PDT     Sunrise
Fri -- 11:33 AM PDT     0.47 feet Low Tide
Fri -- 03:04 PM PDT     Moonset
Fri -- 03:41 PM PDT     2.35 feet High Tide
Fri -- 08:00 PM PDT     Sunset
Fri -- 11:58 PM PDT     -0.08 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Sacramento #4, Sacramento River, California, Tide feet

Clarksburg #4
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Fri -- 03:15 AM PDT     2.41 feet High Tide
Fri -- 03:43 AM PDT     Moonrise
Fri -- 06:06 AM PDT     Sunrise
Fri -- 10:03 AM PDT     0.47 feet Low Tide
Fri -- 02:32 PM PDT     2.35 feet High Tide
Fri -- 03:04 PM PDT     Moonset
Fri -- 08:00 PM PDT     Sunset
Fri -- 10:28 PM PDT     -0.08 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Clarksburg #4, Sacramento River, California, Tide feet

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